This invention generally relates to odor control units or active deodorant devices, air sanitizer units or devices, insecticide vapor units or spray devices, such as liquids, gels or solids, used to control or mask unpleasant odors by evaporating active materials, such as perfume substances, etc. evaporated into the ambient atmosphere, sanitize the air or treat the air with an insecticide. Means may be provided such as a small fan or blower, to work continually or intermittently through electric current or a battery power source, to aid dissipation of the evaporative materials. A difficulty in the use of such devices has been that the consumer did not have a rapid visual means for determining whether (and when) the container is empty. The invention enables a rapid determination to be made as to this by visually observing a container empty flag which will appear automatically only when the active substance has been expended to indicate that the unit is then essentially non-functional and that replenishment should be attended to.
There are, on the market, several devices, generally wall mounted units, intended to be serviced periodically; the drawback in use of such units is that they do not provide an indicator means when the container is empty or in need of servicing. The invention is designed to overcome these and other objections to devices in the prior art by building into the unit a small signalling means, such as a flag, to indicate the empty condition of the container when the active substance in the container has been expended and that it should be refilled to replaced by a new unit. The objectives of the invention may be achieved mechanically or electrically, by mounting the container in a casing suspended balanced on a spring exerting force which, when the container is full, equals the tare weight of the container plus normal contents. As the volatile liquid phase evaporates, the container becomes lighter and will move upwardly responsive to pressure exerted by means such as a spring (or other means) thereupon actuating a mechanism to position the empty signal flag in signalling position.